SLATE COLOR.
To make this color all light colors can be used and some dark ones; only those, however, that do not contain much yellow, as, for example, blues, reds, etc. After preparing for bath by washing and rinsing, or by extracting color if necessary, mix a bath of logwood, about half the usual strength, and enter feathers. Bath must be at boiling temperature, and let them remain in about one minute; after which take out and rinse. Proceed to mix a bath of one quarter ounce of copperas and one gallon of boiling water; enter feathers and let them remain in bath about half a minute; take out and cool off a small portion of the bath, add starch and pass feathers through, squeeze out and dry.
If the color to be matched be very dark, repeat the bath of logwood and mix a bath of one-quarter ounce of bichromate of potash in a gallon of boiling water. Enter feathers and let remain in about half a minute; after which rinse off in cold water, and starch and dry. If a very brilliant shade be required, when you have rinsed feathers from bichromate of potash bath, wash thoroughly in soap-suds and rinse in luke warm water. Dilute a small quantity of starch in cold water, pass feathers through and dry. The above recipe produces a most beautiful shade of slate color, perfectly fast to light, and the depth of shade is regulated by the quantity of logwood. Should you find your color altogether too dark for sample, proceed to extract by passing through a solution of one teaspoonful of oxalic acid to one gallon of boiling water for about half a minute, and then rinsing off twice or three times in boiling water; after which repeat in a milder form.